1. Field of the Invention
The present invention relates to a chain guide that includes a guide shoe that slides and guides a traveling chain, a base member that reinforces the guide shoe along a chain traveling direction, and at least one attachment portion.
2. Description of the Related Art
Conventionally, it is common to use a chain guide including a guide shoe that slides and guides a traveling chain in order to stabilize the chain traveling between sprockets and properly maintain its tension.
For example, as shown in FIG. 64, there is known a timing system of an engine that drives a transmission chain CH such as a roller chain that is endlessly wound around sprockets S1 and S2 provided in a crankshaft and a camshaft in an engine room in which the timing chain CH is endlessly wound around the driving sprocket S1 attached to the crankshaft in the engine room E and a pair of the driven sprockets S2 attached to the camshaft therein, and the timing chain CH is guided by a chain guide 600 (pivoting guide) and a chain guide 500 (fixed guide).
In the known timing system, the chain guide 500 (fixed guide) is fixed in the engine room E with two attachment shafts B1 and B2, and the chain guide 600 (pivoting guide) is attached in the engine room so as to be pivotable about a pivot shaft B0 within a plane of surrounding of the timing chain CH.
A chain tensioner T properly maintains the tension of the timing chain CH and also suppresses vibrations by pressing the chain guide 600 (pivoting guide).
In the chain guide used in the known timing system described above, a traveling guide portion is preferably formed of a material that is low in friction and resistant to wear, and the chain guide entirely formed of a low-friction resin material is known.
However, the chain guide needs some strength, rigidity, and durability for stably guiding the chain against the tension and vibration of the chain and, in a case where the chain guide is formed only of the resin material, it is necessary to increase the thickness and size of the material in order to obtain the required strength, rigidity, and durability so that a space occupied by the chain guide in the engine room is increased.
To cope with this, there is known a chain guide in which the occupied space is reduced while the strength, rigidity, and durability required by the entire chain guide are secured by forming the traveling guide portion with the low-friction resin material and reinforcing the resin material by using a material such as a metal that is high in strength, rigidity, and durability (see Japanese Patent Application Laid-open No. H10-89428 and the like).
For example, as shown in FIGS. 65 to 67, the known chain guide 500 (fixed guide) described in Japanese Patent Application Laid-open No. H10-89428 includes a guide shoe 510 formed of the resin that slides and guides the traveling chain and a base member 520 formed of a plate-like metal that reinforces the guide shoe 510 along the chain traveling direction.
The base member 520 includes a shoe support portion 521 that extends in the chain traveling direction and attachment portions 522 that are disposed at positions spaced apart from each other in the chain traveling direction and extend vertically, and the base member 520 is formed from one metal plate by bending the attachment portions 522 disposed at two positions by 90° with respect to the shoe support portion 521.
The attachment portions 522 at two positions are provided with attachment holes 523 through which bolts and the like are extended.
A traveling guide portion 511 of the guide shoe 510 is supported by the shoe support portion 521 of the base member 520, and the guide shoe 510 can be attached to and detached from the base member 520 by engagement and disengagement of end engaging pieces 512 at both ends in the chain traveling direction and a plurality of side engaging pieces 513 provided at appropriate positions in a width direction with and from the shoe support portion 521.
In the known chain guide described above, since the shoe support portion 521 and the attachment portions 522 at two positions of the base member 520 are formed by bending the same metal plate at two positions by 90°, one metal plate needs to be bent at two positions or more so that a problem has arisen in that the number of manufacturing steps is increased.
In addition, since the shoe support portion 521 and the attachment portions 522 at two positions are constituted by the same metal plate, a problem has arisen in that a large amount of the metal material is required and, since the contour of the base member 520 has many protrusions when the base member 520 is manufactured from one metal plate by punching or the like, a problem has arisen in that the waste of the material is increased.
Further, even in a case where only the positions of the attachment shafts B1 and B2 are changed with the other conditions remaining unchanged, it is necessary to design the base member 520 having a totally different shape, change the shape of the metal plate obtained by punching when the base member 520 is manufactured from one metal plate by punching or the like, and change the positions of bending so that a problem has arisen in that versatility is low in a case where the design of an attachment target is changed or in a case where the chain guide is applied to various attachment targets, and, as a result, manufacturing cost is increased.
Furthermore, in a case where the attachment portion is formed in the base member, it is necessary to use the same material for both of them and make the thicknesses thereof equal to each other so that a problem has arisen in that it is difficult to optimize the design of each of the attachment portion and the base member, and the material cost cannot be reduced.